In a process of manufacturing an automobile, an electronic member, a solar cell, and the like, a fluid such as an adhesive agent, a sealing agent, an insulating agent, a heat releasing agent, and an anti-seizure agent is applied to a workpiece in some cases. A fluid application system is used to apply the fluid to the workpiece. The fluid application system includes: an application apparatus (example: a dispenser) that discharges the fluid to the workpiece; and a movement apparatus (example: an articulated robot) that relatively moves the application apparatus and the workpiece.
The application apparatus includes: a power source (example: a motor): a fluid supply apparatus (example: a pump, an actuator) that changes the supply amount of the fluid per unit time in accordance with the output of the power source; and a nozzle that discharges the fluid supplied from the fluid supply apparatus, to the workpiece. When the fluid is applied to the workpiece, while the fluid is discharged by the application apparatus such that the line width of the fluid on the workpiece is constant, the nozzle is moved in a linear manner, is then moved in an arc-like manner, and is then moved in a linear manner with respect to the workpiece by the movement apparatus in some cases.
FIG. 1 is a schematic diagram illustrating the form of the fluid that is applied to the workpiece in the case where movement of the nozzle with respect to the workpiece is performed in order of a linear manner, an arc-like manner, and a linear manner. In FIG. 1, the region of a fluid 51 applied to a workpiece 50 is indicated by shading, and the application direction is indicated by shaded arrows. If the movement of the nozzle with respect to the workpiece 50 is performed in order of a linear manner, an arc-like manner, and a linear manner, as illustrated in FIG. 1, the fluid 51 applied to the workpiece 50 (hereinafter, also simply referred to as the “applied fluid”) is formed as a first linear part 51a up to a position A, an arc-like part 51b from the position A up to a position B, and a second linear part 51c starting from the position B. On this occasion, the movement speed of the nozzle is changed by the movement apparatus in some cases.
FIG. 2A to FIG. 2D are schematic diagrams illustrating an example of control in the case of changing the movement speed of the nozzle when the movement of the nozzle with respect to the workpiece is performed in order of a linear manner, an arc-like manner, and a linear manner. Of these drawings, FIG. 2A illustrates the relation between the elapsed time and the movement speed. FIG. 2B illustrates the relation between the elapsed time and the rotation speed of the motor (power source) of the application apparatus. FIG. 2C illustrates the relation between the elapsed time and the discharge amount from the nozzle. FIG. 2D illustrates the form of the applied fluid on the workpiece. A position A and a position B illustrated in FIG. 2A to FIG. 2D respectively correspond to the position A and the position B illustrated in FIG. 1. In FIG. 2D, an ideal form of the applied fluid in the case where a response delay in the discharge amount is suppressed is indicated by long dashed double-short dashed lines, and the application direction is indicated by shaded arrows.
As illustrated in FIG. 2A, with respect to the workpiece, the nozzle linearly moves at a high speed in the first linear part, starts decelerating just before the position A that is the end point of the first linear part, and ends decelerating at the position A. After the deceleration end, the nozzle moves at a low speed in the arc-like part. The nozzle starts accelerating at the position B that is the start point of the second linear part, and moves at a high speed after the acceleration end.
In the case of changing the movement speed of the nozzle in this way, for example, if the relative movement speed between the nozzle and the workpiece decreases, in order to make the line width of the applied fluid constant, it is necessary to decrease the discharge amount of the fluid per unit time (hereinafter, also simply referred to as the “discharge amount”) from the nozzle in accordance with the decrease in the movement speed. On the other hand, if the relative movement speed between the nozzle and the workpiece increases, in order to make the line width of the applied fluid constant, it is necessary to increase the discharge amount from the nozzle in accordance with the increase in the movement speed.
Here, in the above-mentioned application apparatus including the power source (example: a motor), the fluid supply apparatus (example: a pump), and the nozzle, if the behavior of the power source is in a stable state, the discharge amount has a positive correlation with the output of the power source (example: the rotation speed of a motor), and the discharge amount increases as the output of the power source increases. Accordingly, in order to control the discharge amount from the nozzle in accordance with a change in the movement speed of the nozzle with respect to the workpiece for the purpose of making the line width of the applied fluid constant, the output of the power source (example: the rotation speed of a motor) may be varied.
Specifically, as illustrated in FIG. 2B, from the state where the rotation speed of the motor is constant, the rotation speed of the motor is decreased in accordance with deceleration in the movement speed of the nozzle, and then the rotation speed of the motor is made constant at the timing at which the movement speed becomes low. After that, the rotation speed of the motor is increased in accordance with acceleration in the movement speed of the nozzle, and then the rotation speed of the motor is made constant at the timing at which the movement speed becomes high.
When the rotation speed of the motor is varied in accordance with a change in the movement speed of the nozzle in this way, a change in the discharge amount takes time to follow a change in the rotation speed of the motor, so that a response delay in the discharge amount occurs. Consequently, the line width of the applied fluid changes, and hence the line width of the applied fluid cannot be made constant.
Specifically, as illustrated in FIG. 2C, the discharge amount of the fluid from the nozzle does not follow a change in the movement speed of the nozzle due to such a response delay. Hence, the line width of the applied fluid is not constant. As a result, as illustrated in FIG. 2D, the line width of the applied fluid is thicker in the arc-like part and part of the second linear part continuous with the arc-like part.
With regard to a fluid application method using the fluid application system including the application apparatus and the movement apparatus, various techniques have been proposed up to now (for example, Japanese Patent No. 5154879 (Patent Literature 1) and Japanese Patent No. 3769261 (Patent Literature 2)). Patent Literature 1 discloses an application method for a liquid material. In this application method, a workpiece placed on a table and a discharge unit including a screw type dispenser opposed to the workpiece are relatively moved at a non-constant speed, and the liquid material is continuously applied with the discharge amount of the liquid material being non-constant. Specifically, when the discharge amount of the liquid material is changed, the rotation speed of a screw is varied up to a predetermined change rate with a constant gradient.
The application method of Patent Literature 1 includes a response time calculation step, a response time adjustment step, and a discharge amount adjustment step, in order to adjust the change start position of the screw rotation speed and the change rate of the screw rotation speed in the course of varying the screw rotation speed. In the response time calculation step, a response delay time at the time of changing the discharge amount is calculated before application start. In the response time adjustment step, the response delay time at the time of changing the discharge amount is adjusted. In the discharge amount adjustment step, the discharge amount is adjusted such that the volume per unit length of the applied liquid material is constant. Patent Literature 1 describes that, in forming an application pattern made of an arc-like part and a linear part, this application method can keep the application amount and the form of the liquid material uniform in the case where the movement speed changes between the arc-like part and the linear part.
Patent Literature 2 discloses a pattern formation method for a display panel. In this pattern formation method, a dispenser discharges a paste while relatively moving with respect to a substrate, whereby a paste layer in a predetermined pattern is formed on the substrate. A screw thread type dispenser or a dispenser including a two-degree-of-freedom actuator (hereinafter, also referred to as the “dispenser with the two-degree-of-freedom actuator”) is used as the dispenser. The dispenser with the two-degree-of-freedom actuator is a dispenser including a first actuator and a second actuator combined with each other. The first actuator linearly drives a piston to thereby generate a positive or negative squeezing pressure on an exit-side end face of the piston. The second actuator rotates the piston on which a screw thread is formed, to thereby generate a pumping pressure and feed a fluid to be applied to the exit side under pressure.
In the case of using the screw thread type dispenser in the pattern formation method of Patent Literature 2, at the time of application start, rotations of the screw thread are accelerated and are then promptly returned to steady rotations. Consequently, kinetic energy that is high enough to overcome a surface tension is given to the fluid immediately after discharge start, and hence the application can be started without forming a clot of the fluid at the leading end of a nozzle. On the other hand, at the time of application end, the rotations of the screw thread are rapidly decelerated and stopped. Consequently, a clot of the fluid at the nozzle leading end can be made as little as possible, and the fluid can be prevented from dripping off at the time of application restart.
Moreover, in the case of using the dispenser with the two-degree-of-freedom actuator in the pattern formation method of Patent Literature 2, at the time of application start, rotations of a motor of a master pump that supplies the paste to the dispenser are started at the same time as the piston is moved downward, and then the dispenser is relatively moved while the motor is rotated, whereby the paste is discharged. Consequently, a precipitous peak pressure (overshoot) occurs in a combined pressure due to a squeezing effect produced along with the downward movement of the piston, and the application can be started without forming a clot of the fluid at the nozzle leading end. Here, the combined pressure is a pressure obtained by adding the squeezing pressure generated by the first actuator including the piston (the exit-side pressure of the first actuator) and the pumping pressure generated by the second actuator of screw type (the exit-side pressure of the second actuator).
On the other hand, at the time of application end, the rotations of the motor are stopped at the same time as the piston is moved upward, and the discharge of the paste is stopped. Consequently, the above-mentioned combined pressure precipitously drops, and a suck-back effect of sucking a clot of the fluid at the nozzle leading end by a slight amount to the inside of the nozzle is obtained. As a result, troubles such as dripping-off of a clot of the fluid can be avoided.
Meanwhile, as illustrated in FIG. 3 to be described below, the line width of the fluid 51 applied to the workpiece 50 is changed halfway in some cases.
FIG. 3 is a schematic diagram illustrating the form of the fluid that is applied to the workpiece in the case where the line width thereof changes halfway. In FIG. 3, the region of the applied fluid 51 on the workpiece 50 is indicated by shading. The line width of the applied fluid 51 illustrated in FIG. 3 changes halfway, and a first thin line part 51d, a thick line part 51e, and a second thin line part 51f appear in the stated order.
The applied fluid 51 made of the first thin line part 51d, the thick line part 51e, and the second thin line part 51f as described above is formed through, for example, the following procedure A of (1) to (3).
(1) With the use of a rectangular flat nozzle having a wide discharge port, the fluid is discharged at the same line width as those of the thin line parts (51d and 51f), and the applied fluid is formed in the region of the first thin line part 51d up to a position C.
(2) Subsequently, after the flat nozzle is moved past the region of the thick line part 51e from the position C up to a position D without applying the fluid to the region of the thick line part 51e, the discharge of the fluid is restarted, and the applied fluid is formed in the region of the second thin line part 51f from the position D.
(3) Lastly, the fluid is discharged at the same line width as that of the thick line part 51e, and the applied fluid is formed in the region of the thick line part 51e from the position C up to the position D.
According to the procedure A as described above, nozzle replacement in the application apparatus is necessary between the time of applying the fluid to the regions of the thin line parts and the time of applying the fluid to the region of the thick line part. In the case of manually performing this nozzle replacement, the replacement work is performed in the state where the apparatus is stopped. Hence, the application interruption time becomes longer, and the manufacture efficiency becomes lower. A nozzle replacement apparatus is used to achieve labor-saving nozzle replacement.
With regard to the nozzle replacement apparatus, various techniques have been proposed up to now (for example, Japanese Patent Application Publication No. 2010-104945 (Patent Literature 3)). Patent Literature 3 discloses a nozzle apparatus with a replacement function usable for fluid application using an application apparatus and a movement apparatus. The nozzle apparatus with the replacement function includes a nozzle with a replacement function, an engaging part, and an engaged part. The nozzle with the replacement function includes: a turn part to which a plurality of nozzles are attached: and a base part that turnably holds the turn part. In order to discharge a fluid supplied from a fluid supply port of the base part from a desired nozzle of the plurality of nozzles, the nozzle with the replacement function can rotationally move the desired nozzle to a predetermined discharge position. The engaging part is provided to the turn part. The engaged part is provided to a fixed-side part, and is disengageably engaged with the engaging part.
In the nozzle apparatus with the replacement function of Patent Literature 3, the base part is moved in the state where the engaging part is engaged with the engaged part, whereby the desired nozzle is rotationally moved to the discharge position. Consequently, a nozzle replacement drive mechanism for rotationally moving the desired nozzle to the discharge position is unnecessary, the application apparatus can be downsized, and apparatus costs can be reduced.